In Canadian Pat. No. 1,130,324 to Vanderhoef, there is described a dead-man control system for a snow blower or like apparatus. Such apparatus has a handle including a horizontal bar portion. The dead-man controls comprised a pair of levers pivotally connected to the handle respective at each side of the horizontal portion. The handles were horizontally elongated and the inwardly facing ends thereof located in proximity whereby they could be grasped by a single hand and retained in their operative position. Such levers were at all times independently operable.
It is known, for example in German OFFEN. No. 2904021 to Miyazawa et al, to provide dead-man levers which are dependently operable in a single hand operation. However, in such system there is no provision for the independent operation of the levers. It is further known, for example, in Canadian Pat. No. 1,154,357 to Hilchey et al to provide dead-man levers that are independently operable, but which may be conjointly operated in a single hand operation by the actuation of a third lever which overlaps the dead-man levers. In such system the dead-man levers must be released prior to the use of the overlapping lever.
Under some circumstances it may be desirable to inactivate one function, while retaining the other function active. An example of such circumstance is where a lawnmower is being self propelled over ground where it is not desired that the cutting blade be rendered operative.
While the foregoing problems could in principle be overcome by the use of sophisticated electronic controls, this would add significantly to the cost of the type of apparatus generally envisaged by the invention, such as lawnmowers and snow blowers, and would be generally non-economic.